The incoming URL determines which responder gets activated.  There are many different types of responders (and more every iteration!)

>SuiteFileSection
>SuiteMoveResponder
>SuitePropertiesResponder
>SuiteRenameResponder
>SuiteRunResponder
>SuiteSearchResponder
>SuiteTestResponders
>SuiteVersionResponder
>TestNameResponder
>TestRssResponder
>TestShutdown
>TestPacketResponder